Integrated circuit (IC) packages such as IC chip carriers commonly comprise a ceramic substrate having oppositely facing parallel major surfaces and peripheral side surfaces. An integrated circuit chip or similar device is mounted on one of the major surfaces and conductors extend from the chip to terminal pads which are located adjacent to the peripheral side surfaces. In some instances, it is desirable to provide terminal pads on both of the major surfaces and possibly circuitry or a circuit device on the second surface. In these instances, conductors must be provided on the side surfaces extending between the terminal pads on the two major surfaces.
A commonly used present manufacturing method comprises the steps of casting a slurry of the ceramic powder containing a binder on a plate to produce a thin sheet of ceramic which, when fired, is coherent and brittle. The binder is driven out during the firing operation and the powders are sintered. Thereafter, one surface of the sheet is scribed with a laser beam to outline blanks, usually square or rectangular, for the substrates. A plurality of blanks are thus outlined and it is possible to carry out steps such as metallization, imaging, plating, resist removal, and etching on an array of blanks during each process. In this manner, a plurality of blanks are produced from each scribed sheet of substrate material and the blanks can then be broken apart for further processing. This method of treating a plurality of blanks results in manufacturing economies over the alternative of producing individual blanks and processing each blank as a single unit.
If the chip carrier requires terminal pads on both surfaces of the substrate and conductors extending across the peripheral side surfaces, the individual substrates must then be further plated to produce the conductors on the side surfaces and the pads on the second surface. The manufacturing cost thus becomes much higher than is the case if conductors are required only on a single surface.
The present widely used manufacturing methods are therefore inconvenient and time consuming, particularly if substrates are being produced having conductors on both surfaces.
It has been recognized that it would be desirable to produce the individual blanks, not by the casting, firing, scribing, and breaking methods described above, but rather by pressing powders in a precision mold to produce the final shape of the blank and then firing the green pressed blank to drive off the binding material and sinter the powders. This alternative production method can yield superior surface finish and also permits the achievement of recesses in one or both of the major surfaces and in the side surfaces. For example, many substrates require a well or recess in the chip receiving zone and it is also necessary to provide recesses in the peripheral side surface for the conductors which may extend between the two major surfaces. Heretofore, the manufacture of the substrate blanks by pressing and sintering has been discouraged by the cost of producing the finished integrated circuit package for the reason that each discrete blank had to be separately handled and treated in all of the metallizing, imaging, plating, etc. processes required. The present invention is directed to the achievement of a manufacturing method which will overcome the disadvantages which have heretofore discouraged the use of discrete blanks in the manufacture of integrated circuit packages. The invention is also directed to the achievement of an improved work holder which is used in the method.